Modified polyester and rubber structures made therefrom

ABSTRACT

Relates to an improved rubber structure reinforced with an improved polyethylene terephthalate reinforcing fiber modified with anthraquinone, a hindered phenol, calcium aluminum silicate, or a polyphenylene ether, the modifier being present with the polyester prior to fiber formation.

United States Patent Bhakuni et a1.

[451 Feb. 19, 1974 MODIFIED POLYESTER AND RUBBER STRUCTURES MADE THEREFROM Inventors: Roop S. Bhakuni, Copley; Joseph L.

Cormany, Jr., Akron, both of Ohio Assignee: The Goodyear Tire & Rubber Company, Akron, Ohio Filed: Feb. 23, 1972 Appl. No.: 228,761

US. Cl 161/144, 156/110 A, 156/110 C, 161/231, 260/45.7 P, 260/45.7 R, 260/45.95, 260/75 T, 260/860 Int. Cl B29h 9/04, C08g 39/10 Field of Search. 260/860, 75 T, 45.7 P, 45.7 R, 260/45.95; 156/110 A, 110 C; 161/231, 144

References Cited UNITED STATES PATENTS 7/1966 Hay 260/47 3,386,952 6/1968 Gleim 260/45.95 3,661,623 5/1972 Bhakuni et al.. 117/76 3,051,212 8/1962 Daniels 260/75 3,563,847 2/1971 Rye et a1 161/176 3,658,637 4/1972 Danielson 161/231 Primary ExaminerWil1iam H. Short Assistant ExaminerEdward Woodberry Attorney, Agent, or Firm-F. W. Brunner 2 Claims, No Drawings MODIFIED POLYESTER AND RUBBER STRUCTURES MADE THEREFROM This invention relates to an improved rubber structure reinforced with an improved polyester reinforcing fiber modified with anthraquinone, a hindered phenol, calcium aluminum silicate or a polyphenylene ether.

Pneumatic tires are being subjected to increasingly severe operating conditions including high speeds and heavy loads. Rubber used in the tire is reinforced with such materials as rayon, nylon, polyester, wire, and glass fibers. Maximum reinforcement of the rubber is obtained with a given fiber when maximum adhesion is produced between the rubber and fiber. Polyethylene terephthalate tire cords are particularly desirable to use as reinforcing elements because of their excellent dimensional stability as shown by low growth or stretch during service. However, it has been observed that in the environment of the rubber of a pneumatic tire the heat generated under high speeds and heavy loads causes the polyester cord to lose its durability, its tensile strength and ultimately its adhesion to the rubber.

The chemical environment of the rubber of a tire is complex because many different chemicals are needed in the construction of the tire in order to obtain maximum tire performance. Because of this chemical complexity in the rubber of the tire and the severe heat developed during service, a variety of chemical reactions may takeplace resulting in by-products that adversely affect the polyester cord.

Many attempts have been made to minimize these adverse effects on the polyester cord such as modifying the rubber, or modifying the adhesive. The present invention is directed to modifying the polyester cord.

It has now been discovered that a more thermally stable pneumatic tire may be made when the rubber thereof is reinforced with a polyester cord modified in the manner described herein.

The thermally stable tire is made possible by the discovery that a polyester cord used in the construction of the pneumatic tire can be protected against tensile loss in the cord and degradation of the adhesive bond between the cord and the rubber by incorporating in the polyester prior to fiber formation a critically small amount of any of the following modifiers:

l. anthraquinone 2. a hindered phenolic phosphorous compound 3. calcium aluminum silicate 4. a polyphenylene ether It is believed that certain desirable reactions take place between certain undesirable by-products present in the polyester and the added modifiers to form a reaction product which is less detrimental to the polyester at elevated temperatures than are the by-products. Although the amounts of modifiers as recited subsequently herein can be used in the practice of the present invention, any of the modifiers described herein can be used in the range of from about 0.01 part to about 2.0 parts by weight of the modifier per 100 parts by weight of the polyester.

Anthraquinone has the following structural formula:

2 The anthraquinone may be used in an amount from about 0.01 part to about 2.0 parts by weight per parts of polyester.

The hindered phenolic phosphorus compounds have the formula:

in which R is a hydrocarbon radical containing from 4 to 10 carbon atoms, P represents the phosphorous atom, and y and z are integers selected from 1 and 2 and the sum of y plus 2 equals 3 and A is selected from the group consisting of HMJQO-P G ll. CHn lOOCGJHah-Q 2 and for convenience referred to as HPP.

Calcium aluminum silicate is also useful to improve the thermal stability of the cord, especially when used as a reinforcing cord in a pneumatic tire. This silicate may be added to the polyester chips in amounts from about 0.1 to 5 parts per 100 parts of polyester.

The polyphenylene ether has the general formula polyphenylene etherthat may be used has the general formula where n has a value such that the melt viscosity of the polymer when measured at 550 F. at a shear rate of 1,500 reciprocal seconds (sec is 2,200 poise and hereinafter referred to as Noryl.

The polyester being modified is any fiber forming thermoplastic linear high molecular weight condensation polyester, and particularly polyethylene terephthalate as well as polymers of cyclohexanedimethylene terephthalate. These polyesters as well as copolyesters of aromatic dicarboxylic acids and particularly condensation products of ethylene glycol with a mixture of terephthalic acid and another dibasic acid such as sebasic or adipic acid or hydroxycarboxylic acid such as parahydroxy benzoic acid present in small amounts and polyesters of terephthalic acid with the glycol l,4-bis(hydroxymethyl) cyclohexane. By linear terephthalic polyesters is meant a linear condensation polyester comprising recurring glycol dicarboxylate structural units in which at least about 85 percent of the recurring structural units are units of the formula wherein G represents a divalent'organic radical containing from about 2 to about 8 carbon atoms which is attached to the adjacent oxygen atoms by saturated carbon atoms. The terephthalate radical may be the sole dicarboxylate constituent of the recurring structural units or up to about percent of the structural units may contain other dicarboxylate radicals such as adipate, sebacate, isophthalate, 4,4 bibenzoate and hexahydroterephthalate. By high molecular weight is meant polyesters having an intrinsic viscosity of at least 0.6 and preferably greater than 0.8 and as high as 1.5 as measured in a 60/40 phenol/tetrachlorethane mixed solvent at 30 C. It is preferred that the polyethylene terephthalate and other similar polyesters have a high melting point which for polyethylene terephthalate is about 265 C. measured with a hot state polarizing microscope. Generally the polyester fibers of this invention may be prepared in accordance with well known procedures for melt extrusion and drafting.

The following examples disclose how an improved polyester cord may be made by adding the modifiers of this invention to polyester chips and then forming filaments therefrom, whichmodified polyester filaments are then gathered into yarn which is then twisted to form a cord.

TABLE I Examples (parts by weight) Ingredients 1 (control) 2 3 4 5 l. Polyethylene I00 [00 W0 100 I00 terephthalate (polyester chips) 2. Anthraquinone 0.1 3. HPP 0.5 4. Calcium 0.2 aluminum silicate 5. Polyphenylene 0.5

ether (Noryl) The dried polyester chips (1) are tumbled with the modifiers (2), (3), (4) and (5) as indicated for Examples 2, 3, 4 and 5 until the mixture is substantially homogeneous. Each blend is then melted in a conventional extruder head and each melt is then spun at. a temperature of about 290 C. through a 190 hole spinneret at a spinning speed of 150 yards per minute to give a single spun yarn having a total denier of approximately 7,800 in accordance with well-known practice used in the melt spinning art and shown in U. S. Pat. Nos. 3,091,510 and 3,097,056. The spun yarn is passed to a pair of rotating heated feed rolls and then passed around a pair of heated draw rolls rotating at a speed to impart a draw ratio of about 6 to l to give a total denier of approximately 1,300 and then would on a bobbin.

The modified polyester yarn had the following properties.

The yarn of Examples 1, 2, 3, 4 and 5 was made into cords (1300/3, 8/8) and treated with conventional R/F/L adhesive made in the following manner, R/F/L being resorcinol/formaldehyde/rubber latex adhesive. A 20 percent solids dispersion of the R/F/L adhesive is made by adding 8.9 parts of resorcinol to 6.55 parts of a 37 percent solution of formaldehyde and 5 parts of a 10 percent solution of sodium hydroxide which is then added to a rubber latex mixture comprising 35.5 parts of a 39.5 percent total solids of the /15/15 terpol ymer of butadiene/styrene/vinyl pyridine and 64 parts of a 40.7 percent total solids of a 70/30 copolymer of butadiene/styrene, the mixture being in 130.05 parts of water. The cords are passed through a dip tank containing this adhesive. The dipped cords are then dried at 450 F. and embedded in rubber compounded as shown below. Peel adhesion test is made of a 1-inch strip under static conditions at 290 F. Thermal stability of the cord is measured in terms of percent tensile retained by the air bomb (AB). Air bomb testing is done by heating the untreated cord embedded in the rubber compound as shown below for 2.5 hours at 350 F. under psi air pressure. The data obtained is listed in Table III.

'7' Table TII Rubber reinforced Peel Mallory Percent Tensile with 22rd from Adhesion Strip Fatigue KC Retained Example ForceRating 1. Control (no 100 100 AB modifier added) 2. Anthraquinone l06 149 l 16 AB 3. HP? 220 109 AB 4. Calcium aluminum 127 I53 l00 AB silicate 5. Polyphenylene 122 188 107 AB ether (Noryl) Peel adhesion is determined in the following manner. Onto the surface ofa l2 mil thick sheet (12"Xl2") of rubber (MRS) is laid the treated cords at the rate of l8 strips of rubber separated by the Holland cloth are then moved in opposite direc- 5 tions at the rate of 2 inches per minute to determine the average force.

2 ASTM-D 885-59T.

The rubber component of the rubber structure of this invention may be any rubber that is a stretchable composition having a tendency to return to its approximate original shape after being vulcanized, and particularly any rubber that is used in the manufacture of tires and drive belts. Thus, the laminate of this invention may involve natural rubber otherwise known as l-levea Brasiliensis, or conjugated diene polymeric rubbers made by polymerizing butadiene-1,3, isoprene, 2,3-dimethyl butadiene-l ,3, and mixtures of these conjugated dienes as well as copolymers of these diene monomers with up to 50 percent of compounds which contain a CH =C= group and which are copolymerizable with butadiene- 1,3 where, for example, at least one of the valences is attached to an electronegative radical, that is a radical which increases the polar character of the molecule such as vinyl, phenyl, nitrile and carboxy radicals. Examples of the diene rubbers are polybutadienes including the stereospecifics, polyisoprenes including the stereospecifics, butadiene/styrene copolymers, also known as SBR, and butadiene/acrylonitrile copolymers also known as NBR.

The control and modified polyester cords of this invention are embedded in rubber compounded in accordance with the following formula:

TABLE IV Parts by Weight Ingredients Amount Used May be Used 1. Natural Rubber 70 0-l00 2. OE/SBR 1778 27.5 [00-0 (styrene/butadienel ,3 23.5/76.5 copolymer) (plus 37% parts oil per 100 SBR) v 3. Cis 1,4-polybutadiene 0-50 4. Carbon Black (Reinforcing 40. 25-100 agent) 5. Zinc Oxide (Activator of 4 2-10 cure) 6. Stearic Acid (Activator of 2 1.5-3.0 cure) 7. Primary Accelerator 1.25 0.5-3.0 (2 2'dithiobisbenzothiazole) 8. Pine Oil (Sofiener) 10 2-50 9. Secondary Accelerator 0.10 0.05-1 .0 (Tetramethylthiuram disulfide) 10. Antioxidant 0.60 0.1-4 1 l. Sulfur (Vulcanizing agent) 2.5 1.0-5.0

In compounding the rubberstock iii'aeaa'rasfic'wnh the formulation set forth above, a master batch of ingredients 1 and 2 are made with the carbon black and mixed on a mill to a temperature of about 1 10 C. and may be mixed at a temperature as high as 140 C. The resulting carbon black master batch is then cooled and the remaining compounds are mixed into the batch in the order indicated above to a temperature of about 70 C. and may be mixed at a temperature as high as 100 C.

The rubber structure of this invention may be prepared by first coating a reinforcing fabric with the rubber and then using the rubber coated fabric to make any desired structure as, for example, a pneumatic tire. The rubber will be compounded in the manner set forth above. The reinforcing fabric may be used without any previous treatment, and under these conditions the fabric is known as grey cord indicating that no treatment in the form of an adhesive composition has been applied to the surface of the cord. Thus, the present invention may be used in the manufacture of a pneumatic tire of conventional present day design as shown, for example, in such U. S. Pat. Nos. as 3,157,218; 3,160,191; 3,160,192; 3,217,778; 3,225,810; 3,225,812; 3,244,215; 3,253,633; and 3,253,638 all of which show a vulcanized rubberized fabric carcass of generally torodial shape having a tread portion super- 5 imposed and bonded to the crown area of the carcass and plies of rubberized fabric forming sidewalls extending from the tread over the carcass to the bead portion.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed is:

1. A heat stable structure comprising vulcanized rubber and a heat stable polyester tire cord, the cord being bonded to the rubber, the cord being made of polyethylene terephthalate fibers melt spun from a mixture comprising polyethylene terephthalate having an I.V. of at least 0.6 measured in a /40 phenol/tetrachlorethane mixed solvent at 30 C., and a modifier selected from the group consisting of anthraquinone, calcium aluminum silicate, a hindered phenol having the general formula r r '1 r 1 0--P--0A [*Q .1. L

wherein R is a hydrocarbon radical 4 to 10C), P is phosphorus, and y and z are integers 1 or 2 and the sum of y and z equals 3 and A is selected from the group consisting of wherein R and R" are the same or different tertiary alkyl radicals (4 to SC), R' is hydrogen or alkyl radicals (2 to 10C) and X is a saturated aliphatic divalent radical (1 to 4C) and a polyphenylene ether having the general formula wherein R is selected from the group consisting of a lower strait chain alkyl radical and a halogen, and n has a value such that the metal viscosity of the polymer is about 2,200 poise when measured at 550 F. at a shear rate of 1,500 sec, wherein the parts by'weight of the modifier per 100 parts by weight of polyester are from about 0.01 part to about 2.0 parts where the modifier is the anthraquinone, 0.025 to parts where the modifier is the hindered phenolic phosphorous compound, from 0.1 to 5 parts where the modifier is calcium aluminum silicate and from 0.1 part to 2.0 parts where the, modifier is the polyphenylene ether.

2. A polyester fiber melt 'spun from a mixture comprising polyethylene terephthalate having an I.V. of at least 0.6, measured in a 60/40 phenol/tetrachlorethane mixed solvent at 30 C. and from about 0.01 part to about 2.0 parts by weight per 100 parts by weight of polyethylene terephthalate of a modifier selected from the group consisting of anthraquinone, calcium aluminum silicate, a hindered phenol having the general formula I F 1 R 0P-OA J. L

wherein R is a hydrocarbon radical (4 to C), I is phosphorous, and y and z are integers l or 2 and the sum of y and 2 equals 3 and A is selected from the group consisting of "wiierearwasa TV are the saiaawa'irraefii tertiary CH5 n wherein R is selected from the group consisting of a lower straight chain alkyl radical and a halogen, and n has a value such that the melt viscosity of the polymer is about 2,200 poise when measured at 550 F. at a shear rate of 'l ,500 sec".

mg?" UNITED sums PATENT OFFICE CERTIFICATE OF CORRECTION Potent No. 3,793, 3 mud February 19, 197

humor) Roop S. Bhakuni" and Joseph L. Cormany, Jr.

It is certified that error appears in the above-identified patent and that and Litton Patent are hereby corrected as shown below:

Column 5', line 2, "rubber cord and rubber cord then" should read rubbervcord and rubber is then Column '7, line 3, "metal viscosity" should read melt viscosit Column 7, lin e ll. "0.1 part to 2.0 parts" should read 0.0l -part to 2.0 parts v Signed andsealed this 3rd day of September 1974. V

(SEAL) v Attest:

MCCOY M. GIBSON, JR. C. MARSHA LL DANN Attesting Officer Commissioner of Patents 

2. A polyester fiber melt spun from a mixture comprising polyethylene terephthalate having an I.V. of at least 0.6, measured in a 60/40 phenol/tetrachlorethane mixed solvent at 30* C. and from about 0.01 part to about 2.0 parts by weight per 100 parts by weight of polyethylene terephthalate of a modifier selected from the group consisting of anthraquinone, calcium aluminum silicate, a hindered phenol having the general formula 